According to the U.S. National Library of Medicine, "Bitter melon is a vegetable used in India and other Asian countries. The fruit and seeds are used to make medicine. People use bitter melon for diabetes, obesity, stomach and intestinal problems, and many other conditions, but there is no good scientific evidence to support these uses." [source]

In beverages, large amounts of juice taken at once or over time have proven to cause gastric distress, or more severe conditions outlined below. Pregnant people should avoid bitter melon, as is the case with many if not most bitter botanicals used in cocktails. As the seeds have been specifically indicated as potentially problematic, it would be best to avoid using these in tinctures and other extractions. 

Safety of Bitter Melon

Much of the scientific literature on bitter melon use focuses on bitter melon supplements, which are typically consumed regularly and in high doses many days in a row, rather than bitter melon as food. In the next section, we learn that respected medical institutions recommend against ingesting the seeds of bitter melon, or drinking large quantities of its juice. 

Danger of Bitter Melon

According to the U.S. National Library of Medicine [source]:

• Pregnancy and breast-feeding: Bitter melon is POSSIBLY UNSAFE when taken by mouth during pregnancy. 
• Diabetes: Bitter melon can lower blood sugar levels. If you have diabetes and take medications to lower your blood sugar, adding bitter melon might make your blood sugar drop too low. Monitor your blood sugar carefully.
• Glucose-6-phosphate dehydrogenase (G6PD) deficiency: A chemical found in bitter melon seeds is related to chemicals in fava beans. Favism is a condition named after the fava bean, which is thought to cause "tired blood" (anemia), headache, fever, stomach pain, and coma in certain people.
• Surgery: There is a concern that bitter melon might interfere with blood sugar control during and after surgery. Stop using bitter melon at least 2 weeks before a scheduled surgery.

According to the Memorial Sloan Kettering Cancer Center, Ingestion of the seeds of bitter melon can cause toxicity to red blood cells, which includes headache, fever, abdominal pain, and coma. Although bitter melon is consumed as food, ingesting the seeds, extracts, and large quantities of juice can cause adverse effects."